Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Family: Apiaceae (Carrot Family)

Synonym(s):

Duration: Biennial, Perennial

Habit: Herb

Listed by:
Invasive Plant Atlas of the US: 1
Federal Noxious Weed: 1
TDA Noxious Weed: 0
TPWD Prohibited Exotic Species: 0

Description: Giant hogweed is a biennial or perennial herb in the carrot family (Apiaceae), growing 15 to 20 feet in height with stout dark reddish-purple stems and spotted leaf stalks. Hollow stalks and stem produce sturdy bristles. The compound leaves with three leaflets may expand to five feet in breadth.

WARNING: Do not touch or handle. Causes severe burning/blistering.

History: Giant hogweed was introduced from Eurasia around 1917 for use as an ornamental plant.

Biology & Spread: Flowers are made up of 50-150 flower rays with small, white florets, that form into an umbrella-shaped flower. Each flower can grow up to 2-1/2 feet in diameter. Each flower ray produce large elliptic dry fruits marked with brown swollen resin canals up to 1 mm in diameter. It flowers from mid-June to mid-July and then produces large flattened elliptic dry seeds with approximately 1500 seeds per flower head.

Ecological Threat: Giant Hogweed is an aggressive competitor. Because of its size and rapid growth, it out-competes native plant species, reducing the amount of suitable habitat available for wildlife. Giant Hogweed dies back during the winter months, leaving bare ground that can lead to an increase in soil erosion on riverbanks and steep slopes.

Giant Hogweed contains a substance within its sap that makes the skin sensitive to ultra violet light. This can result in severe burns to the affected areas, producing swelling and severe, painful blistering. Large, watery blisters usually appear 15 to 20 hours after contact with the sap and sunlight. Contact between the skin and the sap of this species occurs either through brushing against the bristles on the stem (as with a stinging nettle) or breaking the stem/leaves. In the event of contact with the sap of this plant, the skin should be covered to reduce the exposure to sunlight and washed IMMEDIATELY and thoroughly with soap and water.

US Habitat: Giant hogweed can invade a variety of habitats but prefers moist, disturbed soils such as riverbanks, ditches and railroad right-of-ways.

Distribution

US Nativity: Introduced to U.S.

Native Origin: Caucasus (Bailey, L.H. and E.Z. Bailey, Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada, MacMillan Publishing Co., Inc., New York , (1977).); NatureServe Explorer

US States: ME, MI, NY, PA, WA

If you believe you have found a giant hogweed, please report this species.

Resembles/Alternatives: Joe Pye weed (Eutrochium dubium)
Boneset or white snake root (Eupatorium perfoliatum)
Elderberry (Sambucus nigra canadensis)
Southern arrowwood (Viburnum dentatum)

Management: Do not cultivate, plant, purchase, or transplant this plant. It is very difficult to control. If found, notify your state Department of Agriculture, who will handle control measures. Use protective clothing, gloves and face visor or similar to undertake any cutting or removal of this species.

Manual: WARNING: Do not touch or handle. Causes severe burning/blistering. Clear above ground leaf and stem material by hand; remove ground material of roots and seeds.

Chemical: It can be effectively controlled using any of several readily available general use herbicides such as glyphosate early in the season when leaves are less than two feet tall and before the plant flowers and sets seed. Follow label and state requirements.

Biocontrol: Cattle and pigs are cited as possible biocontrol agents. Both eat giant hogweed without apparent harm. Trampling also damages the plant.

USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS. MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.

Listing Source

Texas Department ofAgriculture Noxious Plant List
Texas Parks and Wildlife Department Prohibited Exotic Species
Invaders Program
Federal Noxious Weed
Union of Concerned Scientists
United States Forest Service Southern Research Station

Text References

Swearingen, J., K. Reshetiloff, B. Slattery, and S. Zwicker. 2002. Plant Invaders of Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, 82 pp.

Data Source

www.forestimages.org, http://plants.usda.gov, www.nps.gov/plants/alien,
www.ecy.wa.gov/programs/wq/plants/weeds/aqua012.html,
www.environment-agency.gov.uk,
http://gardening.wsu.edu/column/07-05-98.htm,
www.ceris.purdue.edu/napis/pests/ghw/facts.txt,
https://www.tcweed.org/giant-hogweed-and-cow-parsnip-which-is-which-and-why-you-should-care/

Last Updated: 2023-02-24 by TISI